Substrates for articles such as reflectors for automotive exterior lamp lenses, which require high heat resistance, need to be metallized with metals such as aluminum and tin by processes such as vacuum evaporation and sputtering. Examples of substrates for use in such applications include plastic substrates and metal substrates, such as those made of bulk molding compounds (BMC), polyphenylene sulfides (PPS), aluminum die castings (ALD), polybutylene terephthalate (PBT)/polyethylene terephthalate (PET) alloy resins, polycarbonates (PC), acrylonitrile-butadiene-styrene copolymer (ABS) resins, and polycarbonates (PC) reinforced with fillers such as glass fibers. Recently, plastic substrates have been widely used because of their high heat resistance, their high impact resistance, and particularly, their low weight.
A problem exists, however, in that components manufactured by metallizing heat-resistant plastic substrates with metals such as aluminum tend to have low surface smoothness and lack metallic brightness. In particular, it is difficult to achieve the optical properties required for use as reflectors for automotive headlamp lenses. Accordingly, primers are applied to and cured on the surfaces of the substrates to form a coating layer before metallization to maintain the surface smoothness of the components and thereby achieve improved optical properties (see, for example, PTLs 1 to 4).
However, reflectors for automotive headlamp lenses are composed of a combination of different substrates. For example, whereas a substrate with high heat resistance is used for a portion close to the lamp light source, a substrate with high workability is used for a portion away from the lamp light source, where the shape of the substrate is complicated. To impart adhesion and heat resistance to these substrates, different primers have to be used depending on the type of substrate.
In addition to reflectors for automotive headlamp lenses, numerous metallic-looking components are used for various products to provide a superior design, including cellular phones, automotive parts such as grilles and emblems, cosmetic containers, and household electric appliances. These components are manufactured by forming shaped articles using a combination of various plastics and then metallizing the shaped articles with metals such as tin and aluminum by vacuum evaporation. To form a smooth surface and thereby increase the adhesion between the plastic substrate and the metallized film in this process, there is a need for an actinic-radiation-curable primer applicable to various plastic substrates.